1. Field of the Invention
The present invention relates to an electronic control apparatus for a vehicle, more particularly to an electronic control apparatus configured to supply power to a plurality of electronic control units (ECU) via a relay.
2. Description of the Background Art
Significant development has been seen in vehicles such as automobiles with respect to electronics in view of improving the driving performance, convenience, safety, and the like. Accordingly, the electronic control apparatus for a vehicle is formed of many electronic control units. These ECUs are divided into a plurality of groups based on the control object function and the like.
For example, Japanese Patent Laying-Open No. 2004-064626 (hereinafter, referred to as Patent Document 1) discloses a communication system for a vehicle having an on-vehicle network implemented for each group in an electronic control apparatus including a plurality of ECUs divided into a plurality of groups. Particularly, the configuration disclosed in Patent Document 1 allows data communication to be restored promptly to the proper state when normal data communication is disabled due to communication line disconnection, failure of the gateway device, increase in processing load, and the like.
Power is generally supplied to an ECU via a relay. An electronic control apparatus including a plurality of ECUs employs the configuration in which the plurality of ECUs are divided into a plurality of systems (groups) and an independent relay is arranged for each group in consideration of preventing power cut-off to all the ECUs at the time of relay error and/or from the standpoint of the current capacitance of each relay.
The ON/OFF of the relay is controlled such that power is supplied to each ECU during vehicle operation, and power supply to each ECU is cut-off when the vehicle operation is stopped. Although the electronic control apparatus may be designed such that the power supply initiating timing is slightly deviated between each group in order to prevent excessive starting current at the time of starting the vehicle, each relay basically has its ON/OFF controlled in common with the exception of the starting timing.
There is a rare case where a relay is turned OFF or ON erroneously due to hardware failure or a setting error of an exciting signal directed to controlling the ON/OFF of the relay. In this case, there is a possibility of an ECU being disabled in operation during driving due to power cut-off, or power consumption being wasted continuously to cause the battery to run down due to an ECU being continuously connected to the power source even when the vehicle operation has been stopped.
Such occurrence of a relay on/off error must be quickly detected to effect an appropriate power processing or to notify the driver of such an error. A general method of sensing a relay error includes the step of applying an exciting signal that controls each relay into one ECU, and detecting inconsistency in the logic of the input exciting signals. This method will increase the fabrication cost due to the necessity of a configuration in which a plurality of exciting signals are applied to an ECU, i.e. a configuration with signal lines for transmitting respective exciting signals, port installation at the ECU, and the like.
There is also the problem of how the relay, when a relay error is detected, is to be operated. From the standpoint of continuing the operation of the vehicle, it is desirable to turn ON each relay when a relay error is detected. However, power consumption may be wasted continuously if each relay is unnecessarily ON continuously, leading to the possibility of the battery running down.